Three human lysosomal genes, beta-galactosidase, hexosaminidase A and hexosaminidase B, will be cloned. cDNA's for each will be isolated from a human liver lambda gtll library by screening for antibody reactive plaques. Full-length cDNA's will be isolated and sequenced to establish colinearity with amino acid sequences for each protein. Comparisons with mutants with GM1 and GM2 gangliosidosis will be made after analysis of mRNA and genomic fragments to establish the nucleic acid defects in selected cell lines. Beta-galactosidase cDNA will be inserted into an expression vector and gene therapy will be attempted in beagles with GM1 gangliosidosis.